Testing for biological molecules in food samples:
Benedict's Test (Reducing Sugars)
- Reagent: Benedict's solution (blue)
- Method: Add Benedict's, heat in water bath (80ยฐC)
- Positive result: Blue โ green โ yellow โ orange โ brick red
- Tests for: Glucose, fructose, maltose
Iodine Test (Starch)
- Reagent: Iodine solution (orange/brown)
- Method: Add a few drops to sample
- Positive result: Orange โ blue-black
- Negative result: Stays orange
Biuret Test (Proteins)
- Reagent: Biuret solution (blue)
- Method: Add biuret solution to sample
- Positive result: Blue โ purple
- Negative result: Stays blue
Emulsion Test (Lipids)
- Reagent: Ethanol and water
- Method: Dissolve in ethanol, then add water
- Positive result: White cloudy emulsion forms
- Negative result: Solution stays clear
This required practical covers Required Practical 4: Food Tests within Enzymes in Digestion for GCSE Biology. Enzyme structure and function, digestive enzymes, factors affecting enzyme activity, lock and key model, and practical investigations It is section 8 of 19 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.
Practice questions for Enzymes in Digestion
What are enzymes?
Explain the effect of increasing temperature on enzyme activity.
Quick recall flashcards
What does lipase do?
Breaks down lipids (fats) into fatty acids and glycerol. Produced by pancreas, works in small intestine.
What is an enzyme?
A biological catalyst that speeds up chemical reactions by lowering activation energy. Enzymes are proteins with specific 3D shapes.